In 1982 I invented a reversible drill and drive tool holder which is shown and described in my U.S. Pat. No. 4,512,693 filed Dec. 27, 1982, and issued Apr. 23, 1985. When chucked into the chuck of a high speed electric drill, my reversible tool holder eliminates the inconvenience of multiple chucking and unchucking operations and provides a reversible drill and drive tool holder that is simple to use.
However, the tool holder shown and described in U.S. Pat. No. 4,512,693 comprised three interconnected parts, each requiring considerable machining and thus rather expensive to manufacture.
I have now invented an improved reversible tool holder which includes only two major components and is therefore less expensive to manufacture than my original tool holder. In addition, my improved tool holder can be reversed in less time than my prior tool holder and provides positive locking of the tool into operating position to insure safe operation of either the drill or driving tool.
Basically, my improved tool holder consists of an elongated cylindrical housing and a reversible tool-holding member slidably and pivotably pinned into the cylindrical housing. The cylindrical housing has at its rear end an axial shaft for insertion into the chuck of an electric drill. The front end portion of the housing is bifurcated to form a yoke of the front half of the housing and a pair of elongated slots extend axially along the arms of the yoke.
The tool-holding member has a socket at each end designed to hold a drill bit at one end and a driving tool at the other end. The member is held within the arms of the housing's yoke by a pin. The pin fits into the two elongated slots in the arms of the yoke. The tool-holding member has a pair of flat sides which fit within the inner flat surfaces of the arms of the yoke.
The tool-holding member has identical ends consisting of a cylindrical socket whose outer diameter is the same as the distance between the flat sides of the tool-holding member. Each cylindrical socket is axially bored to receive at one end a drill bit and at the other end a nut driver. A radially-threaded hole in each end of the tool-holding member receives a set screw which secures the drill bit and the nut driver into the sockets at each end of the tool-holding member.
In order to secure the tool-holding member into axial alignment with the axis of rotation of the electric drill, the rear half of the cylindrical housing is machined to provide an axial cylindrical recess into which the cylindrical socket on each end of the tool-holding member can slide as the tool-holding member is slid rearwardly after having been rotated 180.degree. on its pin with the pin slid as far forwardly as it can go within the elongated slots in the arms of the housing's yoke.
The rear portion of the housing is also machined to provide an axial recess which will accommodate the tip end of the drill bit when the tool-holding member is slid backwards along the elongated slot in the yoke's arms. And the rear portion also includes an elongated slot located 90.degree. from the elongated slots in the yoke's arms, which rearwardly located slot provides clearance for the 360.degree. rotation of the drill bit when the tool-holding member is in its most forward position.
In order to secure the tool-holding member in its most rearward position while the drill bit or the nut driver is actually being used, two identical pairs of small indentations are drilled into the two flat-faced sides of the tool-holding member equidistant from and on opposite sides of the pin running through the tool-holding member. Each pair of indentations is designed to be engaged by the ends of two pointed set screws screwed into two radially-threaded holes in the housing when the tool-holding member is in its most rearward position.